Relative vs Absolute risks: Why Relative Risks Are Misleading, and How To Communicate Absolute Risks

The Winton Centre
25 Nov 202004:10
EducationalLearning
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TLDRThe video script discusses the misinterpretation of relative risks in health-related news, using the 1995 UK contraceptive pill scare and the association between processed meat and bowel cancer as examples. It emphasizes the importance of understanding absolute risks and expected frequencies to accurately communicate health risks to the public. The script also introduces an online tool called 'Real Risk' to help translate relative risks into understandable terms.

Takeaways
  • 📢 In 1995, a UK committee's statement on contraceptive pills caused panic due to miscommunication of risks.
  • 💊 The claim that a contraceptive pill doubled the risk of venous thromboembolism was a relative risk, which is difficult to interpret without knowing the absolute risk.
  • 🔢 The absolute risk increase was from 1 in 7,000 to 2 in 7,000 for women taking the pill, which is a small increase.
  • 🌭 Media headlines often use relative risks without context, which can lead to misunderstandings about the actual risks involved.
  • 🥓 An example of this is the association between processed meat and bowel cancer, where a relative risk increase of 18% was reported.
  • 🧐 To understand relative risks, one must know the baseline absolute risk, which for bowel cancer is around 6%.
  • 📈 An 18% increase on a 6% baseline risk leads to a 7% lifetime risk for those consuming extra processed meat daily.
  • 👥 Expected frequencies help put risks into perspective, showing that an extra case of bowel cancer might occur in one out of 100 people due to daily bacon sandwiches.
  • 🥪 Over a lifetime, 100 people eating a bacon sandwich daily might see an increase of about one additional bowel cancer case.
  • 🔄 The main message is to be cautious with relative risks and translate them into absolute risks for better understanding.
  • 🛠️ An online tool called 'Real Risk' can assist in translating relative risks into absolute risks and provide icon arrays for better communication.
Q & A

  • What caused panic among women in 1995?

    -In 1995, thousands of women panicked after the UK Committee for the Safety of Medicines issued a release stating that a certain kind of contraceptive pill doubled the risk of venous thromboembolism, which is a result of a blood clot.

  • What is the difference between relative risk and absolute risk?

    -Relative risk is a measure that compares the risk of an event occurring in one group to the risk in another group. Absolute risk, on the other hand, is the actual number of people who would experience the event within a certain time frame. Understanding absolute risk is crucial for interpreting the significance of relative risk figures.

  • What was the estimated absolute risk of venous thromboembolism for women not taking the contraceptive pill?

    -The estimated absolute risk of venous thromboembolism for women not taking the contraceptive pill was about one in seven thousand.

  • How did the contraceptive pill affect the absolute risk of venous thromboembolism?

    -The contraceptive pill doubled the absolute risk of venous thromboembolism, increasing it from one in seven thousand to two in seven thousand for women taking the pill.

  • What was the public's reaction to the news about the contraceptive pill in 1995?

    -The public's reaction was panic, leading to thousands of women stopping taking their pill, which resulted in a spike in abortions in the UK.

  • What is the main issue with communicating risk using only relative risk figures?

    -The main issue is that relative risk figures can be misleading without the context of absolute risk, as they do not provide a clear understanding of the actual likelihood of an event occurring.

  • How can the risk of eating processed meat, such as bacon or sausages, be better communicated?

    -The risk can be better communicated by translating the relative risk into an absolute risk and expressing it in terms of expected frequencies or the number of people affected out of a certain number of individuals.

  • What was the relative risk increase for bowel cancer associated with eating 50 grams of extra processed meat per day?

    -The relative risk increase for bowel cancer associated with eating 50 grams of extra processed meat per day was 18%.

  • What is the baseline absolute risk of getting bowel cancer for people who eat a normal amount of bacon?

    -The baseline absolute risk of getting bowel cancer for people who eat a normal amount of bacon is around 6%.

  • How many additional cases of bowel cancer can be expected among 100 people who eat an extra bacon sandwich every day?

    -Among 100 people who eat an extra bacon sandwich every day, one additional case of bowel cancer can be expected over the course of their lifetimes.

  • What tool is available to help translate relative risks into absolute risks?

    -An online tool called RealRisk is available to help translate relative risks into absolute risks and can even provide icon arrays for better communication of the risks.

Outlines
00:00
📉 Misinterpretation of Relative Risk in Contraceptive Pill Scare

In 1995, a UK committee's statement that a specific contraceptive pill doubled the risk of venous thromboembolism led to widespread panic among women. The media's use of relative risk without context resulted in a significant spike in abortions as many stopped taking the pill. The actual absolute risk increase was minimal, from one in 7,000 to two in 7,000 among pill users. A better communication strategy would have clarified the actual risk, potentially preventing negative outcomes.

🥓 Misleading Media Reporting on Processed Meat and Bowel Cancer

Media headlines often exaggerate the risks associated with processed meat consumption by using relative risk figures without explaining their significance. A study linked an 18% increased risk of bowel cancer to an additional 50 grams of processed meat daily. However, this relative risk does not convey the actual increase in absolute terms without knowing the baseline risk, which is about 6% for the general population. An 18% increase on this baseline translates to a 1% point increase, meaning one extra case of bowel cancer per 100 people consuming an extra bacon sandwich daily. Understanding this in terms of expected frequencies can provide a more accurate perception of the risk.

Mindmap
Keywords
💡Venous Thromboembolism
Venous thromboembolism (VTE) is a type of blood clot that occurs in the deep veins, usually in the legs, and can travel to the lungs, blocking blood flow and potentially causing a life-threatening condition. In the video, it is mentioned as a risk associated with a certain contraceptive pill, which doubled the risk of VTE, leading to public panic in 1995.
💡Relative Risk
Relative risk is a statistical measure that compares the likelihood of an event occurring in an exposed group to the likelihood of the event occurring in a non-exposed group. It is often used in media reports but can be misleading without context, as it does not provide the actual probability of the event.
💡Absolute Risk
Absolute risk is the difference in the probability of an event between a group that is exposed to a risk factor and a group that is not. It provides a clearer understanding of the actual risk involved, as opposed to relative risk, which only shows the proportionate increase or decrease.
💡Contraceptive Pill
The contraceptive pill is a medication taken orally to prevent pregnancy. It works by releasing hormones that regulate the menstrual cycle and inhibit ovulation. The video discusses a specific type of contraceptive pill that was associated with an increased risk of venous thromboembolism.
💡Processed Meat
Processed meat refers to meat that has been altered from its whole form through processes such as curing, smoking, fermentation, or addition of preservatives. It includes products like bacon, sausages, and deli meats. The video mentions a study linking processed meat consumption to an increased risk of bowel cancer.
💡Bowel Cancer
Bowel cancer, also known as colorectal cancer, is a type of cancer that begins in the large intestine. It is the third most common type of cancer worldwide. The video discusses the link between bowel cancer and the consumption of processed meat.
💡Expected Frequencies
Expected frequencies are the predicted number of occurrences of an event within a specific group or population over a certain period. They are used to provide a clearer picture of risk by translating statistical data into more tangible terms that are easier for the general public to understand.
💡Risk Communication
Risk communication is the process of conveying information about the likelihood and potential consequences of harmful events to the public. It is crucial for public understanding and decision-making, and the video emphasizes the importance of using absolute risks and expected frequencies to effectively communicate health risks.
💡Health Risks
Health risks are potential harms to an individual's health that may result from certain behaviors, environmental exposures, or genetic factors. The video focuses on health risks associated with the use of contraceptive pills and the consumption of processed meat.
💡Media Reporting
Media reporting refers to the way information is presented by various media outlets, which can significantly influence public perception and understanding. The video critiques the media's use of relative risks without providing the necessary context to interpret them accurately.
💡Real Risk Tool
The Real Risk tool is an online resource mentioned in the video that helps translate relative risks into absolute risks and expected frequencies. It provides a visual representation of risks, making it easier for individuals to understand and compare the potential dangers of certain behaviors or exposures.
Highlights

In 1995, a UK committee's statement on contraceptive pills caused widespread panic among women.

The statement claimed that a certain contraceptive pill doubled the risk of venous thromboembolism.

Thousands of women stopped taking their contraceptive pill due to the perceived increased risk.

The result was a significant increase in abortions in the UK.

The claim of doubled risk is an example of relative risk, which can be misleading without context.

Understanding the absolute risk is crucial for interpreting relative risk accurately.

The absolute risk of venous thromboembolism in non-pill users was estimated to be one in seven thousand.

The doubling of risk, from one to two in seven thousand, represents a small absolute increase.

Communicating risks in terms of absolute numbers can prevent unnecessary panic and negative consequences.

Another example of misinterpreted relative risk is the link between processed meat and bowel cancer.

A study found that 50 grams of extra processed meat daily increased bowel cancer risk by 18%.

The baseline absolute risk of bowel cancer for a group eating a normal amount of bacon is about 6%.

An 18% increase over 6% risk results in a 7% lifetime risk for those eating an extra bacon sandwich daily.

Expressing risk as expected frequencies for a group of 100 people can provide clearer perspective.

Out of 100 people eating the normal amount of bacon, six would be expected to get bowel cancer in their lifetime.

For 100 people eating an extra bacon sandwich daily, one additional case of bowel cancer is expected.

100 people eating a bacon sandwich daily consume about 35,000-36,000 sandwiches a year, or 2 million over a hundred lifetimes.

It's important to be cautious with relative risks and, where possible, translate them into absolute risks for better understanding.

An online tool called RealRisk can help translate relative risks into absolute risks and provide icon arrays.

Transcripts

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Risk InterpretationHealth CommunicationContraceptive RisksProcessed Meat DangersBacon & CancerAbsolute vs Relative RiskMedia MisinterpretationHealthcare DecisionsReal Risk ToolPublic Health